Total knee replacement prosthesis

Abstract

A knee replacement prosthesis comprising a femoral component and a tibial component that enable anterior-posterior translation of the femur relative to the tibia and enable the tibia to rotate about its longitudinal axis during flexion of the knee. The femoral component connects to the distal end of a resected femur and includes medial and lateral condyles having distal, articulating surfaces, and a patellar flange having a patellar articulating surface. The tibial component connects to the proximal end of a resected tibia and includes a proximal bearing surface with medial and lateral concavities that articulate with the medial and lateral condyles. The articulating surfaces of the condyles and concavities are defined by sections of toroids.

1. A knee replacement prosthesis having anterior, posterior, lateral, medial, distal and proximal sides and sagital, coronal and transverse planes, comprising:
 a) a femoral component that connects to the distal end of a resected femur, said femoral component including medial and lateral condyles having distal, articulating surfaces with a toroidal anterior surface and a toroidal posterior surface with major and minor axes of rotation, and a patellar flange having an articulating patellar surface; and, 
 b) a tibial component that connects to the proximal end of a resected tibia, said tibial component including a proximal medial and lateral bearing surfaces that articulate with said medial and lateral condyles, respectively, said bearing surfaces having a toroidal anterior surface and a toroidal posterior surface with major radii of curvature that are oriented in different planes; 
 wherein said prosthesis enables anterior-posterior translation of the femur relative to the tibia and enables the tibia to rotate about its longitudinal axis during flexion of the knee. 
 
     
     
       2. The prosthesis recited in  claim 1 , wherein tibial axial rotation is limited to less than about 10 degrees as the knee flexes from full extension to an intermediate position, and tibial axial rotation greater than 10 degrees is enabled as the knee flexes from the intermediate position to full flexion. 
     
     
       3. The prosthesis recited in  claim 2 , wherein the tibia rotates axially less than 10 degrees from full extension to the intermediate position, and more than 10 degrees from the intermediate position to full flexion. 
     
     
       4. The prosthesis recited in  claim 1 , wherein the major radius of curvature of each of the condylar anterior surface and the condylar posterior surface is oriented in the sagital plane, and the minor radius of curvature of each surface is oriented generally in the coronal plane. 
     
     
       5. The prosthesis recited in  claim 1 , wherein the major radii of curvature of the anterior surface and posterior surface of each condyle are unequal, and the minor radii of curvature of the surfaces are equal. 
     
     
       6. The prosthesis recited in  claim 5 , wherein the major radii of curvature of the anterior and posterior surfaces of each tibial bearing surface are unequal and the minor radii of curvature are equal. 
     
     
       7. The prosthesis recited in  claim 6 , wherein the minor radius of curvature of the condylar surfaces is equal to or smaller than the minor radius of curvature of the anterior and posterior surfaces of the tibial bearing surfaces. 
     
     
       8. The prosthesis recited in  claim 1 , wherein the major radius of curvature of the anterior surface of each tibial bearing surface is oriented in the sagittal plane, and the minor radius of curvature is oriented substantially in the coronal or transverse plane. 
     
     
       9. The prosthesis recited in  claim 8 , wherein the major radius of curvature of the posterior surface of each tibial bearing surface is oriented in the transverse plane, and the minor radius of curvature is oriented substantially in the coronal plane. 
     
     
       10. The prosthesis recited in  claim 1 , wherein each of the anterior surfaces of the medial and lateral condyles has a different major radius of curvature, and each of the posterior surfaces of the medial and lateral condyles has a different major radius of curvature. 
     
     
       11. The prosthesis recited in  claim 10 , wherein each of the anterior and posterior surfaces of the medial and lateral condyles has the same minor radius of curvature. 
     
     
       12. The prosthesis recited in  claim 10 , wherein each of the anterior surfaces of the medial and lateral tibial bearing surfaces has a different major radius of curvature, and each of the posterior surfaces of the medial and lateral tibial bearing surfaces has a different major radius of curvature. 
     
     
       13. The prosthesis recited in  claim 12 , wherein said prosthesis is constructed and arranged so that the major radius of curvature of each condylar surface is centered on the axis joining the medial and lateral epicondyles of the femur when said femoral component is connected to the femur. 
     
     
       14. The prosthesis recited in  claim 1 , wherein the medial and lateral tibial bearing surfaces share a single center for the major radius of curvature. 
     
     
       15. The prosthesis recited in  claim 1 , wherein the medial and lateral tibial bearing surfaces have a different center for the major radius of curvature. 
     
     
       16. The prosthesis recited in  claim 1 , wherein each of the anterior surfaces of said condyles has at least a first major radius of curvature in the sagital plane and each of the posterior surfaces has at least a first major radius of curvature in sagital plane that is smaller than the first anterior radius of curvature. 
     
     
       17. The prosthesis recited in  claim 16 , wherein each of the condylar anterior surfaces and posterior surfaces has multiple major radii of curvature in the sagital plane. 
     
     
       18. The prosthesis recited in  claim 17 , wherein each of the anterior and posterior surfaces has the same minor radius of curvature. 
     
     
       19. The prosthesis recited in  claim 1 , wherein each of the anterior surfaces of said tibial bearing surfaces has at least a first major radius of curvature-in the sagital plane and at least a first major radius of curvature in the transverse plane that is larger than the first anterior radius of curvature. 
     
     
       20. The prosthesis recited in  claim 19 , wherein each of anterior surfaces of said tibial bearing surfaces has multiple major radii of curvature in the sagital plane and each of the posterior surfaces has multiple major radii of curvature in the transverse plane. 
     
     
       21. The prosthesis recited in  claim 20 , wherein each of the anterior and posterior surfaces of said tibial bearing surfaces has the same minor radius of curvature. 
     
     
       22. The prosthesis recited in  claim 1 , wherein the condyles translate posteriorly in the tibial bearing surfaces during flexion and anteriorly during extension. 
     
     
       23. The prosthesis recited in  claim 22 , wherein posterior translation is about 1-2 millimeters after the prosthesis is fully flexed. 
     
     
       24. The prosthesis recited in  claim 1 , wherein the posterior portion of each condyle is shaped to allow flexion greater than 100 degrees. 
     
     
       25. The prosthesis recited in  claim 1 , wherein the posterior portion of each condyle is shaped to allow flexion greater than 130 degrees. 
     
     
       26. The prosthesis recited in  claim 1 , wherein said tibial component comprises a base having distal and proximal surfaces, and a liner having a distal surface that engages the proximal surface of the base and a proximal surface forming said bearing surfaces that engages and articulates with the femoral component. 
     
     
       27. The prosthesis recited in  claim 26 , wherein said base comprises a base plate that rests on the tibial plateau, and a keel fixed to the distal surface of the base plate that can be inserted into the proximal tibial medullary canal. 
     
     
       28. The prosthesis recited in  claim 27 , wherein the distal surface of said plate has a textured, roughened surface. 
     
     
       29. The prosthesis recited in  claim 1 , wherein said prosthesis is constructed and arranged to engage the posterior cruciate ligament so that anterior and posterior translation of the femoral component relative to the tibial component is controlled by the patient's posterior cruciate ligament. 
     
     
       30. The prosthesis recited in  claim 29 , wherein contact between the cam and post occurs at knee flexion greater than about 30 degrees. 
     
     
       31. The prosthesis recited in  claim 1 , wherein said prosthesis is constructed and arranged to engage the posterior cruciate ligament so that tibial rotation is controlled by the patient's posterior cruciate ligament. 
     
     
       32. The prosthesis recited in  claim 1 , wherein said femoral component includes a cam connecting the posterior ends of the condyles, and said tibial component includes a central post intermediate said concavities. 
     
     
       33. The prosthesis recited in  claim 32 , wherein anterior and posterior translation of the femoral component relative to the tibial component is controlled by said cam and central post. 
     
     
       34. The prosthesis recited in  claim 32 , wherein rotation of the tibia about its longitudinal axis is controlled by said cam and central post. 
     
     
       35. The prosthesis recited in  claim 1 , wherein said prosthesis is constructed and arranged so that the major radius of curvature of each condylar surface is centered on the axis joining the medial and lateral epicondyles of the femur when said femoral component is connected to the femur. 
     
     
       36. The prosthesis recited in  claim 1 , wherein the anterior and posterior surfaces of each tibial bearing surface are blended smoothly together. 
     
     
       37. The prosthesis recited in  claim 36 , wherein said tibial bearing surfaces are fitted with a patch surface that articulates with said condyles. 
     
     
       38. A knee replacement prosthesis having anterior, posterior, lateral, medial, distal and proximal sides and sagital, coronal and transverse planes, comprising:
 a) a femoral component that connects to the distal end of a resected femur, said femoral component including medial and lateral condyles having a distal, articulating surfaces with a toroidal anterior surface and a toroidal posterior surface with different major and minor axes of rotation, and a patellar flange having an articulating patellar surface; and, 
 b) a tibial component that connects to the proximal end of a resected tibia, said tibial component including a proximal bearing surface with medial and lateral concavities that articulate with said medial and lateral condyles, said concavities having a toroidal anterior surface and a toroidal posterior surface with different major and minor radii of curvature; 
 wherein said prosthesis enables anterior-posterior translation of the femur relative to the tibia and enables the tibia to rotate about its longitudinal axis during flexion of the knee.